Addition Reactions

by Kiley Lynch

So far we’ve talked about acid base reactions, substitution reactions, and eliminations.

Now it’s time to talk about the last major class of reactions you’ll learn in Org 1.  Addition reactions.

These are reactions of alkenes and alkynes. We’ll go into the mechanisms later. For now, make sure you can tell what bonds are forming and breaking.

Here’s a general example of an addition reaction.

 

Notice that we’re breaking a C-C Pi bond and forming two new single bonds to carbon.

This is always the case, by the way. If you’re breaking a C-C Pi bond, it’s an addition reaction.

When you add them all up, there are well over 20 examples of addition reactions  you’ll learn in Org 1,  – including reactions of alkenes and alkynes. But the major difference between them all will simply be in what the identity of the groups “X” and “Y” are.

One last note before we go forward – it will be crucial for you to be able to see the “hidden hydrogens” in alkenes, because they often won’t be drawn in.  Make sure you can figure out number of hidden hydrogens on each of the carbons below.

 

Tomorrow: the Other Russian Rule

Thanks for reading! James
P.S. If you think about it, you might realize that this pattern is the exact opposite of a reaction you’ve already learned: elimination reactions.

elimination : Form C-C Pi , break C-H and C-(Leaving group)

addition: Break C-C Pi, form C-X and C-Y